$K \to πν\barν$搜索中的漏洞\ \& $K_L \to π^0 ν\barν$超越Grossman--Nir Bound
Loophole in $K \to πν\barν$ Search \ \& $K_L \to π^0 ν\barν$ Beyond Grossman--Nir Bound
摘要：
Grossman-Nir界限概念是稳健的，但是可以规避对$K_L \to π^0ν\barν< 1.4 \times 10^{-9}$的常见感知。由于$K\pi2$（3）衰减的盲性，$K^+$衰减实验（如E787/E949和当前运行的NA 62）在运动学上排除了“盲区”。这为目前正在进行的KOTO实验提供了机会。在没有运动学控制的情况下，如果KOTO实验能够否决所有真实背景，它可能会发现$K_L \to π^0 + X^0$，其中$X^0$是一种不可见的“暗”玻色子，质量为$m_{X^0} \sim m_{π^0}$。这可能发生在2015年的数据中，这应该允许KOTO达到标称GN界限灵敏度。给出了规范$L_μ- L_τ$的一个明确模型，它与μ子$g-2$相连，从而与极轻的$Z'$相连.加入与普通夸克混合的类矢量夸克，$W$ -玻色子环会诱导$s\to dZ'$和$b\to sZ'$跃迁。除了实现情景外，该模型还进一步说明了潜在影响。鉴于通常与光子相关的暗玻色子受到严格约束，KOTO有一个独特的机会来探测与μ子相关的暗区。
英文摘要：
The Grossman-Nir bound concept is robust, but the common perception of $K_L \to π^0ν\barν< 1.4 \times 10^{-9}$ may be circumvented. Because of the blinding $K\pi2$(3) decay, $K^+$ decay experiments such as E787/E949 and the currently running NA62 kinematically exclude the "blinding zone". This offers an opportunity for the currently running KOTO experiment. With no kinematic control, if the KOTO experiment is able to veto all true background, it may discover $K_L \to π^0 + X^0$, where $X^0$ is an invisible "dark" boson with mass $m_{X^0} \sim m_{π^0}$. This could happen with 2015 data at hand, which supposedly should allow KOTO to reach nominal GN bound sensitivity. An explicit model of gauged $L_μ- L_τ$, linked with muon $g-2$ hence with very light $Z'$, is given. Adding vector-like quarks that mix with usual quarks, $W$-boson loops induce $s\to dZ'$ and $b\to sZ'$ transitions. Besides realizing the scenario, the model provides further illustration of potential impact. Given that usual dark bosons linked with the photon are tightly constrained, KOTO has a unique opportunity to probe the muon-related dark sector.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
